If the original laser light was red and a crystal is used to double its frequency, the resulting light would fall into the region of the spectrum known as the near-infrared or infrared range.
The red region of the visible light spectrum has a wavelength range of approximately 620 to 750 nanometers. When the frequency of light is doubled, the wavelength is halved. Therefore, the doubled frequency light resulting from red light would have a wavelength range of approximately 310 to 375 nanometers.
This range corresponds to the near-infrared part of the electromagnetic spectrum, which is beyond the range of visible light and is characterized by longer wavelengths than those of visible light but shorter wavelengths than those of microwave radiation.
It's important to note that the exact conversion efficiency and resulting wavelength range may depend on the specific properties of the crystal used for frequency doubling. Different crystals have different capabilities for nonlinear optical processes like frequency doubling, so the resulting wavelength range may vary based on the crystal's characteristics.